Re: [ft-devel] Modification in FT_Gzip_Uncompress

[Werner LEMBERG]

> In OpenType fonts, SVG documents can be either in plain text or gzip
> encoded.
> 
> While writing the code to read these documents I looked for a
> function which could do gzip decoding inside FreeType.  That's when
> I found `FT_Gzip_Uncompress'.  Using it, I realized it didn't work
> as expected and returned errors.
> 
> After using zlib in a separate program on the same data I figured
> out the problem.  Zlib data can be encoded with both `gzip' and
> `zlib' encoded wrapper.  AFAIK, by default, it looks for only `zlib'
> wrapper. The current call to `inflateInit2' is:
> 
> 749|  err = inflateInit2( &stream, MAX_WBITS );
>
> `MAX_WBITS' is 15.  Thus, it only looks for `zlib' wrapper and in
> case of gzip compressed SVGs, returns error when `inflate' is
> called.  The fix is to replace it with:
> 
> 749|  err = inflateInit2( &stream, MAX_WBITS|32 );
>
> This enables both `gzip' and `zlib' decoding with automatic header
> detection.  Solving my problem.

Great!

> This solves it for me and I HOPE this won't cause cause any previous
> code relying on `FT_Gzip_Uncompress' to fail.  Let me know if there
> are easy tests to check that.
> 
> Let me know if this is the right change and can also be made in
> master later on, meaning I can rely on it. :)

Please prepare a patch for master.  In case there are problems I guess
that the FreeType fuzzers will catch them, probably unveiling hidden
bugs.


    Werner